JP2012058338A - Optical element, camera module, and mobile device - Google Patents

Abstract

PROBLEM TO BE SOLVED: To provide an optical element which is used in a camera mechanism of a mobile device and is capable of improving the image quality without using a mechanical driving mechanism.SOLUTION: The optical element includes a first transparent substrate 11, polarizing means 12 which is provided on the light incidence side of the first transparent substrate 11 and transmits light having a specific polarization direction out of incident light, and a liquid crystal lens element 13 provided between the first transparent substrate 11 and the polarizing means 12. The liquid crystal lens element 13 includes: a liquid crystal layer 14 having liquid crystal molecules aligned in the same direction as the specific polarization direction; a transparent insulating layer 15 which is provided on the light incidence side of the liquid crystal layer 14 and in contact with the liquid crystal layer 14; and first and second transparent electrodes 16 and 17 to which voltages for controlling the alignment state of the liquid crystal molecules in the liquid crystal layer 14 are applied, where the first transparent electrode 16 is provided in contact with the first transparent substrate 11 and the liquid crystal layer 14 and the second transparent electrode 17 is provided in contact with the transparent insulating layer 15 and the polarizing means 12.

Description

  The present invention relates to an optical element mounted on a mobile device such as a mobile phone, a camera module including the optical element, and a mobile device.

  In recent years, portable devices such as mobile phones are often equipped with small camera mechanisms. In general, the camera mechanism is preferably equipped with a polarizing filter function that removes the influence of reflected light according to the use environment and a focal length adjustment function according to the distance to the subject. Quality improvement can be realized.

  In order to realize such a polarization filter function and a focal length adjustment function, a mechanical drive mechanism is used. For example, Patent Document 1 discloses a camera module that varies and adjusts a focal length using a mechanical drive mechanism that moves a lens in an optical axis direction by a coil.

JP 2008-185913 A

  However, providing the mechanical drive mechanism as described above is not preferable because it leads to an increase in the size of the portable device.

  Therefore, an object of the present invention is to provide an optical element that can be used in a camera mechanism of a portable device and can improve image quality without using a mechanical drive mechanism, and a camera module and a portable device including the optical element. That is.

  In order to achieve the above-described object, the optical element of the present invention is provided on the light incident side with respect to the first transparent substrate and the first transparent substrate, and has a specific polarization direction among the incident light. Liquid crystal molecules having a polarizing means for transmitting light, and a liquid crystal lens element provided between the first transparent substrate and the polarizing means, wherein the liquid crystal lens element is aligned in the same direction as a specific polarization direction A liquid crystal layer, a transparent insulating layer provided in contact with the liquid crystal layer on the light incident side with respect to the liquid crystal layer, and a first voltage to which a voltage for controlling the alignment state of the liquid crystal molecules of the liquid crystal layer is applied A second transparent electrode, wherein the first transparent electrode is provided in contact with the first transparent substrate and the liquid crystal layer, and the second transparent electrode is provided in contact with the transparent insulating layer and the polarizing means. And first and second transparent electrodes.

  The camera module of the present invention includes the optical element described above, and the portable device of the present invention includes the camera module described above.

  As described above, according to the present invention, there are provided an optical element that can be used in a camera mechanism of a portable device and can improve image quality without using a mechanical drive mechanism, a camera module including the optical element, and a portable device. be able to.

It is a schematic sectional drawing of the optical element in the 1st Embodiment of this invention. It is a schematic plan view of the 1st and 2nd transparent electrode of the optical element in the 1st Embodiment of this invention. It is a schematic sectional drawing of the optical element in the 2nd Embodiment of this invention. It is a schematic sectional drawing of the optical element in the 3rd Embodiment of this invention. It is a schematic perspective view of the optical element in the 4th Embodiment of this invention.

  Embodiments of the present invention will be described below with reference to the drawings.

[First Embodiment]
FIG. 1 is a cross-sectional view schematically showing the configuration of the optical element according to the first embodiment of the present invention, and shows a cross section along the stacking direction.

  The optical element 10 of the present embodiment is used in the front stage of an image pickup element (not shown) of a camera module, and includes a first transparent substrate 11, a polarizing plate (polarizing means) 12, a first transparent substrate 11, and a polarization. And a liquid crystal lens element 13 provided between the plate 12.

  The first transparent substrate 11 is made of a glass plate, and a first transparent electrode 16 to be described later is formed on the surface on the light incident side (the upper side in FIG. 1). The polarizing plate 12 is provided on the light incident side with respect to the first transparent substrate 11 and the liquid crystal lens element 13, and is used to transmit light having a specific polarization direction out of the light incident on the optical element 10. ing. As a result, an image of a distant view of the subject becomes clearer, and unnecessary reflection on the subject due to reflected light from the water surface or glass can be prevented.

  The liquid crystal lens element 13 includes a liquid crystal layer 14, a transparent insulating layer 15 provided in contact with the liquid crystal layer 14 on the light incident side with respect to the liquid crystal layer 14, and first and second layers provided so as to sandwich these layers. Second transparent electrodes 16 and 17. The first transparent electrode 16 is provided in contact with the first transparent substrate 11 and the liquid crystal layer 14 on the first transparent substrate 11 side, and the second transparent electrode 17 is transparently insulated on the polarizing plate 12 side. It is provided in contact with the layer 15 and the polarizing plate 12.

  The liquid crystal layer 14 has liquid crystal molecules aligned in a predetermined direction by rubbing treatment, and the alignment direction of the liquid crystal molecules is set to be the same as the polarization direction of the light transmitted through the polarizing plate 12. ing. Thereby, the light of the specific polarization component transmitted through the polarizing plate 12 is incident on the liquid crystal layer 14, and the focal length in the liquid crystal layer 14, that is, the liquid crystal lens element 13 can be adjusted. The transparent insulating layer 15 is provided as a thin film such as glass in order to adjust the distance between the liquid crystal layer 14 and the second electrode 17.

  FIG. 2 is a plan view schematically showing the first transparent electrode 16 and the second transparent electrode 17, FIG. 2 (a) is a schematic plan view of the first transparent electrode 16, and FIG. 3 is a schematic plan view of a second transparent electrode 17. FIG.

  The first and second transparent electrodes 16 and 17 are each made of a transparent conductive film such as indium tin oxide (ITO). As shown in FIG. 2A, the first transparent electrode 16 formed on the first transparent substrate 11 is so-called solid so as to cover the entire surface on the light incident side of the first transparent substrate 11. It is configured as a pattern. On the other hand, as shown in FIG. 2B, the second transparent electrode 17 formed on the transparent insulating layer 15 includes a circular electrode 17a in the vicinity of the center and a periphery formed so as to surround the periphery of the circular electrode 17a. And an electrode 17b. The circular electrode 17a and the peripheral electrode 17b are electrically insulated from each other and have the same potential inside. Therefore, the second transparent electrode 17 is configured to be able to control the electrodes 17a and 17b by individually applying a voltage to them.

  With such a configuration, the liquid crystal lens element 13 can realize a focal length adjustment function by controlling only two kinds of voltage values. That is, the first voltage applied between the first transparent electrode 16 and the surrounding electrode 17b and the second voltage applied between the first transparent electrode 16 and the circular electrode 17a are adjusted. By doing so, the alignment state of the liquid crystal molecules of the liquid crystal layer 14 can be controlled so that the focal length adjustment function is realized. Specifically, the liquid crystal layer 14 can be provided with a function as a lens by the first voltage, and in that state, a second voltage independent of the first voltage is variably applied. The focal length can be adjusted according to the perspective of the subject.

  As described above, in the optical element 10 of the present embodiment, the polarization filter function and the focal length adjustment function related to image quality can be realized without using a mechanical drive mechanism. As a result, it is possible to form an image that is clearer than the conventional image on the image sensor and record the image while maintaining the miniaturization and thinning of the camera module.

[Second Embodiment]
FIG. 3 is a cross-sectional view schematically showing the configuration of the optical element according to the second embodiment of the present invention, and shows a cross section along the stacking direction.

  The present embodiment is a modification in which the configuration of the polarization means on the light incident side is changed with respect to the first embodiment. In the optical element 20 of the present embodiment, instead of the polarizing plate 12 in the first embodiment, a glass plate 22a, and a polarizing film 22b set so that the polarization direction is the same as the alignment direction of the liquid crystal layer 14 A polarizing means 22 is provided. Other configurations are the same as those in the first embodiment, and the effects obtained by this embodiment are also the same as those in the first embodiment. In addition, in each embodiment shown below including this embodiment, the same code | symbol is attached | subjected to drawing about the same member as 1st Embodiment, and description is abbreviate | omitted.

[Third Embodiment]
FIG. 4 is a cross-sectional view schematically showing a configuration of an optical element according to the third embodiment of the present invention, and shows a cross section along the stacking direction.

  This embodiment is a modification of the first embodiment, and several layers for freely selecting the polarization plane of incident light are added.

  In the first embodiment, since the liquid crystal lens element imparts a lens effect only to a polarization component in one specific direction, the vibration direction of the polarization plane of light passing through the liquid crystal lens element is defined by the polarization direction of the polarizing plate. The direction will be limited. When light having a desired polarization plane is desired to pass, it is conceivable to rotate the entire element including the polarizing plate and the liquid crystal lens element. However, this requires a mechanical rotation mechanism. Will lead to an increase in size. On the other hand, in this embodiment, as will be described later, by providing a mechanism for rotating the polarization plane of incident light, light having a desired polarization plane can be passed without using a mechanical rotation mechanism. Is possible.

  That is, the optical element 30 of the present embodiment includes a second transparent substrate 31 provided on the light incident side further than the polarizing plate 12 in addition to the configuration of the first embodiment, and the second transparent substrate. And an optical rotation means 32 provided between 31 and the polarizing plate 12.

  The optical rotator 32 includes a TN liquid crystal layer 33 that rotates the polarization plane of incident light, and third and fourth transparent electrodes 34 and 35 to which a voltage for controlling the rotation is applied. . The third transparent electrode 34 is provided in contact with the polarizing plate 12 and the TN liquid crystal layer 34, and the fourth transparent electrode 35 is provided in contact with the TN liquid crystal layer 34 and the second transparent substrate 31. . The third and fourth transparent electrodes 34 and 35 are made of the same transparent conductive film as the first and second transparent electrodes 16 and 17, respectively.

  The TN liquid crystal layer 33 is constituted by rubbing treatment so that the alignment directions of liquid crystal molecules are orthogonal to each other by upper and lower transparent plates (not shown). Therefore, the liquid crystal molecules in the layer are twisted by 90 degrees and arranged. Yes. In this state, the polarization plane of the light transmitted through the TN liquid crystal layer 33 is rotated by 90 degrees, that is, the TN liquid crystal layer 33 exhibits optical activity. In the present embodiment, when a voltage is applied to the TN liquid crystal layer 33 through the third and fourth transparent electrodes 34 and 35, the alignment direction of the liquid crystal molecules in the TN liquid crystal layer 33 can be changed. The amount of rotation of the polarization plane of the light passing through 33 can be changed. Therefore, by adjusting the strength of the applied voltage between the electrodes 34 and 35, it is possible to control the amount of rotation of the polarization plane and change the degree of optical rotation. In this way, in the present embodiment, the relative angle between the polarization plane of the transmitted light by the optical rotation means 32 and the polarization direction of the polarizing plate 12 is adjusted, and the camera module (liquid crystal lens element 13) is adjusted according to the use situation. The angle of the polarization plane of incident light can be controlled. This makes it possible to obtain the same effect as the polarization filter effect obtained by rotating the polarizing plate by simply applying a voltage without using a mechanical drive mechanism, and adjusting the sharpness and light amount of the subject image. Is possible. The TN liquid crystal layer 33 is set so that the alignment direction on the polarizing plate 12 side is the same as the polarizing direction of the polarizing plate 12 (that is, the alignment direction of the liquid crystal layer 14).

  In the optical rotation means 32 of the present embodiment, the polarization plane of incident light can be obtained only by applying one kind of voltage between the third and fourth electrodes 34 and 35 of a solid pattern (not shown). It is also advantageous that the vibration direction can be freely controlled. Further, the first and third transparent electrodes 16 and 34 or the first and fourth transparent electrodes 16 and 35 may be electrically connected to be at the same potential. The above-described effects can be obtained only by controlling the types of voltages independently. Therefore, the control method is very simple and the pattern of each electrode is very simple, so that the manufacturing cost can be kept low.

[Fourth Embodiment]
FIG. 5 is a perspective view schematically showing a configuration of an optical element in the fourth embodiment of the present invention. For the sake of simplicity, some components are not shown.

  The present embodiment is a modification to the third embodiment, and the optical element 40 of the present embodiment is a flexible member that electrically connects the second transparent electrode 17 and the third transparent electrode 34. A flexible printed circuit board (FPC) 41 that is a wiring member is provided. Further, on the FPC 41, an integrated circuit (IC) 42 which is an AC voltage applying means for applying an AC voltage between the second and third transparent electrodes 17 and 34 is provided. The IC 42 is driven by a DC power supply having a voltage of 5 V or less, and thus can be driven by a power supply voltage of a small camera or a mobile phone. For this reason, the optical element 40 of the present embodiment can be controlled by voltage of optical characteristics without providing a new power supply mechanism, and can be easily mounted on a small portable device. In the present embodiment, the first transparent electrode and the second transparent electrode are electrically connected so as to have the same potential, and similarly, the third transparent electrode and the fourth transparent electrode. Are electrically connected so as to have the same potential.

  In the present embodiment, the second transparent electrode 17 and the third transparent electrode 17 provided on the upper surface and the lower surface of the polarizing plate 12, respectively, are formed by cutting out the sheet-like FPC 41 and bending the cut-out portion 41a. An electrical connection with the transparent electrode 34 is obtained. For this reason, this embodiment can also contribute to reduction of manufacturing cost.

10, 20, 30, 40 Optical element 11 First transparent substrate 12 Polarizing plate 13 Liquid crystal lens element 14 Liquid crystal layer 15 Transparent insulating layer 16 First transparent electrode 17 Second transparent electrode 17a Circular electrode 17b Ambient electrode 22 Polarizing means 22a Glass plate 22b Polarizing film 31 Second transparent substrate 32 Optical rotation means 33 TN liquid crystal layer 34 Third transparent electrode 35 Fourth transparent electrode 41 Flexible printed circuit board (FPC)
42 Integrated Circuit (IC)

Claims (9)

A first transparent substrate;
A polarizing means provided on the light incident side with respect to the first transparent substrate and transmitting light of a specific polarization direction among the incident light;
A liquid crystal lens element provided between the first transparent substrate and the polarizing means;
Have
The liquid crystal lens element is
A liquid crystal layer having liquid crystal molecules aligned in the same direction as the specific polarization direction;
A transparent insulating layer provided in contact with the liquid crystal layer on the light incident side with respect to the liquid crystal layer;
The first and second transparent electrodes to which a voltage for controlling the alignment state of the liquid crystal molecules in the liquid crystal layer is applied, wherein the first transparent electrode includes the first transparent substrate and the liquid crystal layer. First and second transparent electrodes, wherein the second transparent electrode is provided in contact with the transparent insulating layer and the polarizing means, and
An optical element.   The first transparent electrode is formed so as to cover the entire surface on the light incident side of the first transparent substrate, and the second transparent electrode surrounds the circular electrode and the periphery of the circular electrode. The optical element according to claim 1, comprising a peripheral electrode formed and electrically insulated from the circular electrode. A second transparent substrate provided on the light incident side with respect to the polarizing means; and an optical rotation means provided between the polarizing means and the second transparent substrate,
The optical rotation means includes a TN liquid crystal layer that rotates a polarization plane of incident light, and third and fourth transparent electrodes to which a voltage for controlling the rotation is applied, wherein the third transparent electrode The third and fourth transparent layers are provided in contact with the polarizing means and the TN liquid crystal layer, and the fourth transparent electrode is provided in contact with the TN liquid crystal layer and the second transparent substrate. The optical element according to claim 1, comprising an electrode. The first and second transparent electrodes are electrically connected to have the same potential, and the third and fourth transparent electrodes are electrically connected to have the same potential;
A flexible wiring member that electrically connects the second transparent electrode and the third transparent electrode; and an AC voltage provided between the second and third transparent electrodes provided on the wiring member. The optical element according to claim 3, further comprising: an alternating voltage applying unit that applies.   The optical element according to claim 4, wherein the AC voltage applying means is driven by a DC power supply having a voltage of 5 V or less.   The optical element according to claim 1, wherein the polarizing means is a polarizing plate.   The said polarizing means has a 3rd transparent substrate, and the polarizing film provided in contact with this 3rd transparent substrate on the incident side with respect to this 3rd transparent substrate on light. The optical element according to any one of the above.   A camera module comprising the optical element according to claim 1.   A portable device comprising the camera module according to claim 8.

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